(a) Field of the Invention
The present invention relates to an optical fiber fitting and, more particularly, to the locking structure of an optical fiber fitting used for introducing an optical fiber into an optical device.
(b) Description of the Related Art
An optical device, such as an optical repeater used for a submarine cable in an optical communication system, may be associated with an optical fiber fitting having an encapsulation structure or airtight structure and used for introducing optical fibers into the optical device.
FIG. 1 shows an example of a conventional optical fiber fitting. The optical fiber fitting, generally designated by numeral 10A, includes a metallic sleeve 11 fixed to an optical repeater (shown by dotted line), which is disposed at the front end of the fitting 10A, i.e., the bottom of the fitting 10A in the figure. A metallic rod 17 mounting thereon optical fibers 12 has a part received within the metallic sleeve 11.
FIG. 2 shows the structure of the interior of the metallic sleeve 11, whereas FIG. 3 shows the metallic sleeve of FIG. 2 in a front view thereof. The metallic sleeve 11 is of a hollow cylinder, the front end of which is provided with a front plug 16 formed as a unitary body therewith, as shown in FIG. 2. The front plug 16 is used as a stopper for the metallic rod 17. A flange member 14 is provided on the outer surface of the metallic sleeve 11 in the vicinity of the front end of the metallic sleeve 11 for fixing the optical fiber fitting 10A onto the optical device. Four through-holes 15 are formed in the front plug 16 of the metallic sleeve 11 in this example, as shown in FIG. 3, for allowing four optical fibers to pass therethrough.
FIG. 4 is a side view of the metallic rod 17, and FIG. 5 is the front view thereof. The metallic rod 17 has a front cylinder 17A received within the metallic sleeve 11, a rear cylinder (or rear disk) 17B disposed outside the metallic cylinder 11 and having thereon a plurality of fiber channels 19 arranged at a constant angular pitch, and a coupling column 17C coupling together the rear cylinder 17A and the front cylinder 17B. As illustrated in FIG. 5, the rear cylinder 17B has four fiber channels 19 on the outer periphery thereof.
The optical fibers 12 shown in FIG. 1 are received in the respective fiber channels 19 of the rear cylinder 17B, and also received in respective channels 21 formed on the outer surface of the front cylinder 17A of the metallic rod 17. The channels 19 and 21 of the metallic rod 17 extend in the axial direction of the optical fiber fitting 10A. The optical fiber 12 is stripped of the overcoat between the rear cylinder 17B and the front cylinder 17A of the metallic rod 17 to expose the core of the optical fiber 12.
FIG. 1 illustrates the combination structure wherein the metallic rod 17 attached with optical fibers 12 are received in the metallic sleeve 11. For obtaining the combination structure of FIG. 1, the optical fibers 12 are first fixed onto the metallic rod 17 shown in FIG. 4, and then inserted into the metallic sleeve 11 together with the metallic rod 17. Before this step, the forward portions of the optical fibers 12 to reside below the channels 21 of the metallic rod 17 are allowed to pass through the respective through-holes 15 of the metallic sleeve 11 in advance toward the interior of the optical device. The metallic rod 17 of FIG. 4 is attached with the optical fibers 12 in advance, which are fixed onto the rear cylinder 17B of the metallic rod 17 with adhesive 23.
The front cylinder 17A of the metallic rod 17 is forwarded to be stopped by the rear surface of the front plug 16, and adhered thereto with adhesive 24. Subsequently, the rear portion of the gap between the inner surface of the metallic sleeve 11 and the outer periphery of the coupling column 17C of the metallic rod 17 is filled with a low-melting-point metal 25 for airtight.
In the conventional encapsulation structure of the optical fiber fitting 10A as described above, the work efficiency for obtaining the combination structure is relatively low due to the difficulty in the step of allowing the optical fibers 12 to pass through the respective through-holes 15 formed in the front plug 16.
In view of the above, it is an object of the present invention to provide a locking structure of an optical fiber fitting, which is capable of encapsulating optical fibers for airtight without a complicated work.
The present invention provides an optical fiber fitting including: a cylindrical sleeve having an inner surface, the inner surface having thereon a first annular groove extending normal to an axial direction of the cylindrical sleeve; a ring-like spring member having a radially outer surface received in the first annular groove, with a radially inner surface of the spring member protruding from the first annular groove; and a rod member having a cylindrical portion received in the cylindrical sleeve, the cylindrical portion having thereon at least one channel extending along the axial direction for receiving therein an optical fiber and a second annular groove extending normal to the axial direction and receiving therein the radially inner surface of the spring member, the spring member locking the rod member with the cylindrical sleeve.
In accordance with the optical fiber fitting of the present invention, the rod member and the cylindrical sleeve are locked by the function of the ring-like spring member and thus the front plug of the cylindrical member is not needed. This obviates the step of allowing the optical fibers to pass through the respective through-holes of the front plug of the cylindrical sleeve, and improves the work efficiency in the assembly of the optical fiber fitting.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.